1. Technical Field
The present application relates generally to nanotube fabrics and methods of making same.
2. Discussion of Related Art
As ultra-large-scale-integration of integrated circuits, microelectronic components and devices are becoming increasingly more dense and compact, there exists an increasing need for smaller and more potent heat transfer devices due to the excessive on-chip heat generation. Current integrated circuits used in microprocessors operated at high frequencies use power densities on the order of 50 W/cm2: in comparison, a 60 W light bulb generates 0.5 W/cm2. Such power densities lead to highly localized heating of integrated circuits in areas known as “hot spots”.
As the rise in power density increases, the number of “hot spots” on the surface of high power chips increases as observed in microprocessors. Cooling microprocessors is generally necessary to prevent device degradation and to achieve the best possible device performance. A maximum safe temperature for integrated circuit (IC) operation is typically between 100-120° C.
Solving the problems that “hot spots” present is imperative for the next-generation IC packages, as there is an ever-increasing need for smaller-scale devices. Carbon nanotubes (CNTs) are being used in many different applications in the field of electronics and are found to be extremely useful due to their electrical, mechanical, optical, chemical and thermal properties.
Carbon nanotubes, with tube diameters around 1-2 nm, are electrical conductors that are able to carry extremely high current densities. They also have the highest known thermal conductivity, and are also generally thermally and chemically stable. Further details on characteristics of carbon nanotubes may be found in the following references, the entire contents of which are incorporated herein by reference: Z. Yao, C. L. Kane, C. Dekker, Phys. Rev. Lett. 84, 2941 (2000); P. M. Ajayan, T. W. Ebbesen, Rep. Prog. Phys. 60, 1025 (1997); Savas Berber, Young-Kyun Kwon and David Tománek, “Unusually High Thermal Conductivity of Carbon Nanotubes,” Phys. Rev. Lett. 84(20), 4613-4616 (2000); Jianwei Che, Tahir Cagin and William A Goddard III, “Thermal conductivity of carbon nanotubes,” Nanotechnology, 11, 65-69, 2000; J. Hone, M. Whitney and A Zettl, “Thermal conductivity of single-walled carbon nanotubes,” Synthetic Metals, 103-2498-2499, 1999 and Mohamed A Osman and Deepak Srivastava, “Temperature dependence of the thermal conductivity of single-wall carbon nanotubes,” Nanotechnology, 12, 21-24, 2001.
Using individual nanotubes for heat transfer, however, can be problematic because of difficulties in growing them with suitably controlled orientation, length, and the like.
There is a need in the art for very efficient, very small, even submicron-sized, heat transfer elements which are easily fabricated and are compatible with electronics applications and fabrication techniques. There is likewise a need in the art for large scale fabrication methods of heat transfer devices used for electronic applications in the semiconductor industry which can be monolithically integrated into a CMOS or similar process flow to fabricate integrated circuits. Naturally, the uses of such elements extend to most types of consumer electronics where heat transfer in integrated elements is beneficial.